It has been known that an organic polymer having at least one reactive silicon group has such an interesting property that it is crosslinked as a result of the formation of siloxane bonds accompanying the hydrolysis reaction of the reactive silicon group in the presence of moisture even at room temperature, thus obtaining a rubber-like cured article.
Among these polymers having a reactive silicon group, a polyoxyalkylene polymer and a polyisobutylene polymer are disclosed in Japanese Kokai Publication No. Sho-52-73998, Japanese Kokai Publication No. Hei-5-125272, Japanese Kokai Publication No. Hei-3-72527, Japanese Kokai Publication No. Sho-63-6003, Japanese Kokai Publication No. Sho-63-6041, Japanese Kokai Publication No. Hei-1-38407 and Japanese Kokai Publication No. Hei-8-231758. Particularly, the polyoxyalkylene polymer and the polyisobutylene polymer have already been produced industrially and widely used in applications such as sealing materials, adhesives, and paints.
In case the organic polymer is a saturated hydrocarbon polymer, the cured article is useful as sealing materials for buildings and sealing materials for double glazings because it is excellent in heat resistance, water resistance and weatherability. Furthermore, an isobutylene polymer containing a repeating unit originating in isobutylene in the total amount of 50% by weight or more is suited for use as moisture-proofing sealing materials because it is excellent in low moisture permeability and low gas permeability.
Since these sealing materials are generally used for the purpose of imparting watertightness and airtightness by filling into the joint or clearance between various members, its conformability to the portion to be applied for a long time is very important and it is required to exhibit sufficient elongation and strength.
In case such an organic polymer having a reactive silicon group is cured with crosslinking, a silanol condensation catalyst is used and also an amine compound such as laurylamine is often used as a promoter for the purpose of promoting the condensation reaction. As the silanol condensation catalyst, tin catalysts, for example, divalent tin such as tin octylate (2-ethylhexanoate) and tetravalent tin such as dibutyltin bisacetylacetonate are widely used. In case the portion where the sealing material is installed moves drastically, divalent tin is often used because a cured article having recovery properties is obtained.
However, in case divalent tin such as tin octylate is used in combination with a promoter such as amine compound, as a curing catalyst of the component (A), the resulting cured article is sometimes insufficient in strength and elongation, and thus it is required to further improve physical properties.
Almost all of the latter tetravalent tin catalysts are dibutyltin type catalysts and are widely used because the resulting cured article has relaxation property, i.e. property capable of following a long-term change in stress applied from the outside, and rapid curability and also it can be applied as a curing catalyst of a one-part curable composition. However, since toxicity becomes a problem when a small amount of tributyltin is contained therein, it is required to develop a tin-free silanol condensation catalyst.
In Japanese Kokoku Publication No. Sho-35-2795, Japanese Kokoku Publication No. Sho-32-3742, Japanese Kokoku Publication No. Sho-35-9639, and Japanese Kokoku Publication No. Sho-37-3271, carboxylic acid salts of tin and various tin-free carboxylic acid metal salts are disclosed as a curing catalyst of an organopolysiloxane composition. As an example wherein a tin-free carboxylic acid metal salt is used as a curing catalyst of a composition containing an organic polymer having a reactive silicon group, bismuth carboxylate (Japanese Kokai Publication No. Hei-5-39428 and Japanese Kokai Publication No. Hei-9-12860) and cerium carboxylate (Japanese Kokai Publication No. 2000-313814) are listed. However, there has never been studied intensively about various carboxylic acid metal salts.